The present invention relates to an intravascular imaging guidewire system and to methods for use and manufacture thereof, and more specifically to an imaging guidewire which can be used to receive a therapeutic catheter having a guide lumen to direct the catheter to a desired position within a vessel of a body.
Intraluminal, intracavity, intravascular, and intracardiac treatment and diagnosis of medical conditions utilizing minimally invasive procedures is an effective tool in many areas of medical practice. These procedures are typically performed using imaging and treatment catheters that are inserted percutaneously into the body and into an accessible vessel of the vascular system at a site remote from the vessel or organ to be diagnosed and/or treated, such as the femoral artery. The catheter is then advanced through the vessels of the vascular system to the region of the body to be treated. The catheter may be equipped with an imaging device, typically an ultrasound imaging device, which is used to locate and diagnose a diseased portion of the body, such as a stenosed region of an artery. The catheter may also be provided with a therapeutic device, such as those used for performing interventional techniques including balloon angioplasty, laser ablation, atherectomy and the like. Catheters also are commonly used for the placement of grafts, stents, stent-grafts, etc., for opening up and/or preventing closure of diseased or damaged vessels.
Catheters having ultrasound imaging and/or therapeutic capabilities are generally known. For example, U.S. Pat. No. 5,313,949, issued to Yock, the disclosure of which is incorporated herein by reference, describes an intravascular ultrasound imaging catheter having an atherectomy cutting device. Generally speaking, there are two predominant techniques used to position the therapeutic catheter at the region of interest within the body. The first technique simply involves directly inserting the catheter into a vessel and advancing the catheter through the branches of the vascular system by pushing and steering the catheter to enter a desired branch as the catheter is moved forward. The use of this technique typically requires that the catheter be equipped with an extremely flexible guidewire at its distal tip that can be aimed in different directions by rotating the catheter or by actuating a steering mechanism.
The second technique utilizes a separate guidewire that is first positioned within the vascular system such that a distal end of the guidewire extends beyond the region of interest. The guidewire is routed into position by inserting it into a vessel and advancing it through the vascular system by pushing and steering the guidewire similar to the method previously described for a catheter. The catheter being inserted includes a guidewire lumen that is sized to receive the guidewire. The guidewire lumen may extend the entire length of the catheter, or alternatively, the guidewire lumen may be a short length lumen disposed at the distal end of the catheter. Once the guidewire is in place, the therapeutic and/or imaging catheter is routed over the guidewire to the region of interest while holding the guidewire fixed in place.
The use of a guidewire provides several advantages. Routing a catheter or guidewire through a circuitous path of the complex network of blood vessels to a region of interest can be a tedious and time consuming task. Placement of the guidewire is made even more difficult with increasing vessel occlusion that may occur in the later stages of vascular disease. In addition, many catheter procedures require the use of several different catheters. For instance, an imaging catheter may be initially inserted to precisely locate and diagnose a diseased region. Then, the imaging catheter may be removed and a therapeutic catheter, such as an balloon angioplasty catheter, may be inserted. Additional therapeutic or imaging catheters may be employed as necessary. Accordingly the successive insertion and removal of each of these catheters, called catheter xe2x80x9cexchanges,xe2x80x9d is required because there is only enough space within the vessels to rout a single catheter at a time. Hence, with the use of a guidewire, the tedious and time-consuming task of routing a device to the region of interest need only be done once. Then, the much easier procedure of routing catheters over the guidewire to the region of interest may be performed as many times as the desired therapy dictates.
In order to locate the site of interest and facilitate proper placement of the guidewire, and further to observe the site during and after treatment, a guidewire may include an imaging device, commonly a rotating ultrasonic imaging transducer or a phased-array ultrasound transducer. Providing the guidewire with imaging capability may eliminate the need for insertion of an imaging catheter or imaging capabilities in the therapeutic catheters. Hence, an imaging guidewire can reduce the number of catheter exchanges that a physician must do during a surgical procedure.
Imaging guidewires have been disclosed generally as, for example, in U.S. Pat. No. 5,095,911, issued to Pomeranz, the disclosure of which is incorporated herein by reference. The imaging guidewire disclosed in Pomeranz includes an elongate, flexible body. A housing enclosing a rotating transducer is secured to the distal end of the body. A drive shaft extends through a lumen of the body and is coupled to the transducer. In order to image a different region of interest, the entire guidewire is moved back and forth to position the housing and transducer adjacent the region.
However, once the physician has carefully placed the imaging guidewire, it is preferable to maintain the guidewire in a fixed position so as not to lose the correct placement of the guidewire. At the same time, it is often desirable to obtain images along an axial length of diseased area. This currently requires axial translation of the imaging device by axially translating the entire guidewire. The problem with advancing and pulling back the imaging guidewire is that the correct placement of the guidewire may be lost and the physician must then spend more time repositioning the guidewire.
Furthermore, there are significant technical obstacles in producing an imaging guidewire having a sufficiently small diameter to fit within a guidewire lumen of a catheter while at the same time exhibiting the necessary mechanical and electrical characteristics required for placement in the vascular system and generation of high quality images. For instance, on typical catheters sized to be inserted in the smaller coronary vessels, the guidewire lumen preferably is sized to receive a guidewire having a maximum diameter of 0.014xe2x80x3. However, where larger vessels, such as peripheral vessels, are to be imaged, the guidewire lumen may be sized to receive a guidewire having, for example, a maximum diameter of 0.035xe2x80x3. In addition, the guidewire preferably has sufficient flexibility to traverse a tortous path through the vascular system, and also has sufficient column strength, or pushability, to transmit a pushing force from a remote proximal end of the guidewire, along a winding path, to the distal end thereof.
Moreover, if a rotating transducer is utilized, the drive shaft extending to the transducer should have stable torsional transmittance in order to achieve high quality images. Hence, the drive shaft should not only be flexible, but also should be torsionally stiff to limit angular deflection and nonuniform angular velocity that can cause image distortion. The drive shaft also should be mechanically and electrically connectable to a drive unit and to transducer signal processing electronics. The connection preferably is easily disconnectable so that a guidewire lumen of a catheter may be threaded over the proximal end of the guidewire. This requirement also limits the size of the connector on the drive shaft because the connector must also fit through the guidewire lumen. The drive shaft and connector also should provide a high quality transmission of imaging signals between the imaging device and the signal processing equipment.
Therefore, a need exists for an improved imaging guidewire that overcomes the aforementioned obstacles and deficiencies of currently available guidewires.
The present invention provides an intravascular imaging guidewire, and methods of use and manufacture, which can accomplish longitudinal translation of an imaging plane allowing imaging of an axial length of a region of interest without moving the guidewire thereby maintaining proper positioning of the guidewire to effectively facilitate the introduction of catheters over the guidewire to the proper position. The imaging guidewire disconnectably mates to a drive unit. The drive unit acts as an interface and connects to signal processing equipment which comprises electronics to transmit, receive and process imaging signals to and from the imaging guidewire.
Accordingly, the imaging guidewire of the present invention comprises a body in the form of a flexible, elongate tubular member. An elongate, flexible imaging core is preferably slidably and rotatably received within the body. Rotation and longitudinal translation of the imaging core is preferred in order to provide a 360xc2x0 scan, but it is contemplated in the present invention that the imaging core may also be non-rotating, for example an imaging core having a phased-array ultrasound transducer.
The imaging core includes a rotatable drive shaft having an imaging device mounted on its distal end. The imaging device produces an imaging signal that can be processed by the signal processing equipment to create an image of the feature at which the imaging device is directed. An electrical cable runs through the center of the drive shaft extending from the imaging device at the distal end to a connector attached to the proximal end of the drive shaft. The connector detachably connects the driveshaft to a drive unit and electrically connects the electrical cable to the drive unit and in turn to the signal processing equipment. At least a distal portion of the body through which the imaging device images preferably is substantially transparent to imaging signals received by the imaging device. The transparent portion of the body preferably extends for at least an axial length over which imaging typically will be desirable.
The body and the imaging core are cooperatively constructed to enable axial translation of the imaging core and imaging device relative to the body. This allows imaging along an axial length of a diseased region in the patient""s body without moving the guidewire body.
As described above, the imaging guidewire connects to a drive unit. The principle function of the drive unit is to provide an interface between the imaging guidewire and the signal processing equipment. The drive unit, therefore, transmits the imaging signal between the imaging guidewire and the signal processing equipment. In a further aspect of the present invention, in the preferred embodiment comprising a rotating transducer, the drive unit has a motor to rotate the imaging core for providing a 360xc2x0 scan. In an alternative embodiment, the motor for rotating the imaging core may be part of the signal processing equipment. In this case, the drive unit simply has a drive shaft that is detachably coupled to the motor of the signal processing equipment.
In a further aspect, a coupling device, such as a slip ring assembly or an innovative inductive or capacitive coupling in accordance with one aspect of the present invention, may be provided in the drive unit or within an associated adapter to transmit the imaging signals from the rotating electrical cable within the guidewire drive shaft to the non-rotating electronics within the drive unit. In an alternative embodiment having the motor in the signal processing equipment, the coupling device may be contained in the signal processing equipment.
In a particularly innovative alternative embodiment, the connector on the proximal end of the drive shaft is adapted to provide only a mechanical connection to the mating connector on the drive unit or adapter. For a rotating imaging core, the mechanical connection transmits torque from the drive unit or adapter to the imaging core. In this embodiment, the imaging signal is transmitted from the imaging guidewire connector to the drive unit or adapter via a capacitive coupling or inductive coupling. One element of the coupling is disposed on the draft shaft and rotates with the drive shaft. The other element of the coupling is mounted in the drive unit or adapter and may be rotating or non-rotating.
As is suggested above, in an additional aspect of the present invention, an adapter may be utilized which performs the function of providing an interface between the imaging guidewire and the drive unit. The adapter comprises a connector which mates to the imaging guidewire connector. The imaging guidewire connector plugs into the adapter which in turn mounts into the drive unit. In the preferred embodiment, the adapter makes both the mechanical and the electrical connections to the imaging guidewire. Furthermore, the coupling device of the drive unit may be contained in the adapter instead. In this way, the coupling device transmits the imaging signals from the rotating electrical cable within the guidewire drive shaft to non-rotating electronics within the adapter. Mounting the adapter into the drive unit electrically connects the adapter to the drive unit, for example via mating electrical connectors.
In the preferred method of using the imaging guidewire of present invention, the imaging guidewire is first inserted percutaneously into a vessel of the vascular system, usually at a site remote from the site of interest within the body. The imaging guidewire is routed to the region of interest by advancing it through the branches of the vascular system by pushing and steering the guidewire as the guidewire is fed into the vessel. The imaging device may be activated during this process to aid in routing the guidewire and locating a diseased region of the body. The imaging guidewire is positioned such that the distal end extends beyond the diseased region with the transparent portion of the body approximately centered at the region of interest.
Alternatively, a standard guidewire may first be inserted and routed to the region of interest. Then, a catheter having a full-length guidewire lumen is fully inserted over the standard guidewire. The standard guidewire is then removed and the imaging guidewire is inserted through the guidewire lumen to the desired position.
At this point, in order to image the length of the diseased region, the imaging device may be axially translated forward and back relative to the body which is preferably fixed in place.
Once the medical condition has been diagnosed and a treatment is chosen, a therapeutic catheter having a guidewire lumen, or a series of therapeutic catheters, may be routed over the guidewire to the diseased region to perform the desired treatment. To facilitate the catheter exchanges over the guidewire, the imaging guidewire is disconnected from the drive unit by simply disconnecting the guidewire connector from the drive unit. Once the exchange is complete, the imaging guidewire is reconnected to the drive unit. The imaging device on the guidewire may further be used to monitor the treatment while it is being performed and/or to observe the treated area after the treatment is completed. Alternatively, if the imaging device cannot image through the therapeutic catheter, the catheter may be pulled back to expose the imaging device.
Accordingly, it is an object of the present invention to provide an improved imaging guidewire and method of using the same.
A further object of the present invention is to provide an improved imaging guidewire that can image along an axial length of a region of interest while maintaining a fixed guidewire position.